After the Ammophilae, the paralysers who multiply their lancet-thrusts
to destroy the influence of the various nerve-centres, excepting those
of the head, it seemed advisable to interrogate other insects which also
are accustomed to a naked prey, vulnerable at all points save the
head, but which deliver only a single thrust of the sting. Of these two
conditions the Scoliae fulfilled one, with their regular quarry, the
tender Cetonia-, Oryctes-or Anoxia-larva, according to the Scolia's
species. Did they fulfil the second? I was convinced beforehand that
they did. From the anatomy of the victims, with their concentrated
nervous system, I foresaw, when compiling my history of the Scoliae,
that the sting would be unsheathed once only; I even mentioned the exact
spot into which the weapon would be plunged.
These were assertions dictated by the anatomist's scalpel, without the
slightest direct proof derived from observed facts. Manoeuvres executed
underground escaped the eye, as it seemed to me that they must always
do. How indeed could I hope that a creature whose art is practised in
the darkness of a heap of mould would decide to work in broad daylight?
I did not reckon upon it all. Nevertheless, to salve my conscience,
I tried bringing the Scolia into contact with her prey under the
bell-glass. I was well-advised to do so, for my success was in inverse
ratio to my hopes. Next to the Philanthus, none of the Hunting Wasps
displayed such ardour in attacking under artificial conditions. All the
insects experimented upon, some sooner, some later, rewarded me for my
patience. Let us watch the Two-banded Scolia (S. bifasciata, VAN DER
LIND) operating on her Cetonia grub.
The incarcerated larva strives to escape its terrible neighbour. Lying
on its back, it fiercely wends its way round and round the glass circus.
Presently the Scolia's attention awakens and is betrayed by a continued
tapping with the tips of the antennae upon the table, which now
represents the accustomed soil. The Wasp attacks the game, delivering
her assault upon the monster's hinder end. She climbs upon the
Cetonia-grub, obtaining a purchase with the tip of her abdomen. The
quarry merely travels the more quickly on its back, without coiling
itself into a defensive posture. The Scolia reaches the fore-part,
with tumbles and other accidents which vary greatly with the amount
of tolerance displayed by the larva, her improvised steed. With her
mandibles she nips a point of the thorax, on the upper surface; she
places herself athwart the beast, arches herself and makes every effort
to reach with the end of her abdomen the region into which the sting
is to be driven. The arch is a little too narrow to embrace almost the
whole circumference of her corpulent prey; and she renews her
attempts and efforts for a long time. The tip of the belly tries every
conceivable expedient, touching here, there and everywhere, but as yet
stopping nowhere. This persistent search in itself demonstrates the
importance which the paralyser attaches to the point at which her lancet
is to penetrate the flesh.
Meanwhile, the larva continues to move along on its back. Suddenly it
curls up; with a stroke of its head it hurls the enemy to a distance.
Undiscouraged by all her set-backs, the Wasp picks herself up, brushes
her wings and resumes her attack upon the colossus, almost always by
mounting the larva's hinder end. At last after all these fruitless
attempts, the Scolia succeeds in achieving the correct position. She
is seated athwart the Cetonia-grub; the mandibles grip a point on the
dorsal surface of the thorax; the body, bent into a bow, passes under
the larva and with the tip of the belly reaches the region of the neck.
The Cetonia-grub, placed in serious peril, writhes, coils and uncoils
itself, spinning round upon its axis. The Scolia does not interfere.
Holding the victim tightly gripped, she turns with it, allows herself to
be dragged upwards, downwards, sidewards, following its contortions. Her
obstinacy is such that I can now remove the bell-glass and follow the
details of the drama in the open.
Briefly, in spite of the turmoil, the tip of the abdomen feels that the
right spot has been found. Then and only then the sting is unsheathed.
It plunges in. The thing is done. The larva, at first plump and active,
suddenly becomes flaccid and inert. It is paralysed. Henceforth there
are no movements save of the antennae and the mouthparts, which will for
a long time yet bear witness to a remnant of life. The point wounded
has never varied in the series of combats under glass: it occupies
the middle of the line of demarcation between the prothorax and the
mesothorax, on the ventral surface. Note that the Cerceres, operating on
Weevils, whose nervous system is as compact as the Cetonia-grub's,
drive in the needle at the same spot. Similarity of nervous organization
occasions similarity of method. Note also that the Scolia's sting
remains in the wound for some time and roots about with marked
persistence. Judging by the movements of the tip of the abdomen, one
would certainly say that the weapon is exploring and selecting. Free to
shift in one direction or the other, within narrow limits, its point is
most probably seeking for the little mass of nerve-tissue which must
be pricked, or at least sprinkled with poison, to obtain overwhelming
paralysis.
I will not close this report of the duel without relating a few further
facts, of minor importance. The Two-banded Scolia is a fierce persecutor
of the Cetonia. In one sitting the same mother stabs three larvae, one
after the other, in front of my eyes. She refuses the fourth, perhaps
owing to fatigue or to exhaustion of the poison-bag. Her refusal is only
temporary. Next day, she begins again and paralyses two grubs; the day
after that, she does the same, but with a zeal that decreases from day
to day.
The other Hunting Wasps that pursue the chase far afield grip, drag,
carry their prey, after depriving it of movement, each in her own
fashion and, laden with their burden, make prolonged attempts to escape
from the bell-glass and to gain the burrow. Discouraged by these futile
endeavours, they abandon them at last. The Scolia does not remove her
quarry, which lies on its back for an indefinite time on the actual spot
of the sacrifice. When she has withdrawn her dagger from the wound, she
leaves her victim where it lies and, without taking further notice
of it, begins to flutter against the side of the glass. The paralysed
carcase is not transported elsewhere, into a special cellar; there where
the struggle has occurred it receives, upon its extended abdomen, the
egg whence the consumer of the succulent tit-bit will emerge, thus
saving the expense of setting up house. It goes without saying that
under the bell-glass the laying does not take place: the mother is too
cautious to abandon her egg to the perils of the open air.
Why then, recognizing the absence of her underground burrow, does the
Scolia uselessly pursue the Cetonia with the frantic ardour of the
Philanthus flinging herself upon the Bee? The action of the Philanthus
is explained by her passion for honey; hence the murders committed in
excess of the needs of her family. The Scolia leaves us perplexed: she
takes nothing from the Cetonia-grub, which is left without an egg; she
stabs, though well aware of the uselessness of her action: the heap of
mould is lacking and it is not her custom to transport her prey. The
other prisoners, once the blow is struck, at least seek to escape with
their capture between their legs; the Scolia attempts nothing.
After due reflection, I lump together in my suspicions all these
surgeons and ask myself whether they possess the slightest foresight,
where the egg is concerned. When, exhausted by their burden, they
recognize the impossibility of escape, the more expert among them ought
not to begin all over again; yet they do so begin a few minutes later.
These wonderful anatomists know absolutely nothing about anything, they
do not even know what their victims are good for. Admirable artists
in killing and paralysis, they kill or paralyse at every favourable
opportunity, no matter what the final result as regards the egg.
Their talent, which leaves our science speechless, has not a shadow of
consciousness of the task accomplished.
A second detail strikes me: the desperate persistence of the Scolia. I
have seen the struggle continue for more than a quarter of an hour, with
frequent alternations of good luck and bad, before the Wasp achieved the
required position and reached with the end of her abdomen the spot where
the sting should penetrate. During these assaults, which were resumed as
soon as they were repulsed, the aggressor repeatedly applied the tip of
her belly to the larva, but without unsheathing, as I could see by the
absence of the start which the larva gives when it feels the pain of the
sting. The Scolia therefore does not prick the Cetonia anywhere until
the weapon covers the requisite spot. If no wounds are inflicted
elsewhere, this is not in any way due to the structure of the larva,
which is soft and vulnerable all over, except in the head. The point
sought by the sting is no more unprotected than any other part of the
skin.
In the scuffle, the Scolia, curved into a bow, is sometimes seized by
the vice-like grip of the Cetonia-grub, which is violently coiling and
uncoiling. Heedless of the powerful grip, the Wasp does not let go for
a moment, either with her mandibles or with the tip of her abdomen. At
such times the two creatures, locked in a mutual embrace, turn over and
over in a mad whirl, each of them now on top, now underneath. When it
contrives to rid itself of its enemy, the larva uncoils again, stretches
itself out and proceeds to make off upon its back with all possible
speed. Its defensive ruses are exhausted. Formerly, before I had seen
things for myself, taking probability as my guide I willingly granted to
the larva the trick of the Hedgehog, who rolls himself into a ball and
sets the Dog at defiance. Coiled upon itself, with an energy which my
fingers have some difficulty in overcoming, the larva, I thought, would
defy the Scolia, powerless to unroll it and disdaining any point but
the one selected. I hoped and believed that it possessed this means of
defence, a means both efficacious and extremely simple. I had presumed
too much upon its ingenuity. Instead of imitating the Hedgehog and
remaining contracted, it flees, belly in air; it foolishly adopts the
very posture which allows the Scolia to mount to the assault and to
reach the spot for the fatal stroke. The silly beast reminds me of
the giddy Bee who comes and flings herself into the clutches of the
Philanthus. Yet another who has learnt no lesson from the struggle for
life.
Let us proceed to further examples. I have just captured an Interrupted
Scolia (Colpa interrupta, LATR.), exploring the sand, doubtless in
search of game. It is a matter of making the earliest possible use of
her, before her spirit is chilled by the tedium of captivity. I know her
prey, the larva of Anoxia australis (The Anoxia are a genus of Beetles
akin to the Cockchafers.--Translator's Note.); I know, from my past
excavations, the points favoured by the grub: the mounds of sand
heaped up by the wind at the foot of the rosemaries on the neighbouring
hill-sides. It will be a hard job to find it, for nothing is rarer than
the common if one wants it then and there. I appeal for assistance to my
father, an old man of ninety, still straight as a capital I. Under a sun
hot enough to broil an egg, we set off, shouldering a navvy's shovel
and a three-pronged luchet. (The local pitchfork of southern
France.--Translator's Note.) Employing our feeble energies in turns, we
dig a trench in the sand where I hope to find the Anoxia. My hopes are
not disappointed. After having by the sweat of our brow--never was the
expression more justified--removed and sifted two cubic yards at least
of sandy soil with our fingers, we find ourselves in possession of two
larvae. If I had not wanted any, I should have turned them up by the
handful. But my poor and costly harvest is sufficient for the moment.
To-morrow I will send more vigorous arms to continue the work of
excavation.
And now let us reward ourselves for our trouble by studying the tragedy
in the bell-glass. Clumsy, awkward in her movements, the Scolia slowly
goes the round of the circus. At the sight of the game, her attention
is aroused. The struggle is announced by the same preparations as those
displayed by the Two-banded Scolia: the Wasp polishes her wings and taps
the table with the tips of her antennae. And view, halloo! The attack
begins. Unable to move on a flat surface, because of its short and
feeble legs, deprived moreover of the Cetonia-larva's eccentric means
of travelling on its back, the portly grub has no thought of fleeing; it
coils itself up. The Scolia, with her powerful pincers, grips its skin
now here, now elsewhere. Curved into a circle with the two ends almost
touching, she strives to thrust the tip of her abdomen into the narrow
opening in the coil formed by the larva. The contest is conducted
calmly, without violent bouts at each varying accident. It is the
determined attempt of a living split ring trying to slip one of its ends
into another living split ring, which with equal determination
refuses to open. The Scolia holds the victim subdued with her legs
and mandibles; she tries one side, then the other, without managing to
unroll the circle, which contracts still more as it feels its danger
increasing. The actual circumstances make the operation more difficult:
the prey slips and rolls about the table when the insect handles it too
violently; there are no points of purchase and the sting cannot reach
the desired spot; the fruitless efforts are continued for more than an
hour, interrupted by periods of rest, during which the two adversaries
represent two narrow, interlocked rings.
What ought the powerful Cetonia-grub to do to defy the Two-banded
Scolia, who is far less vigorous than her victim? It should imitate
the Anoxia-larva and remain rolled up like a Hedgehog until the enemy
retires. It tries to escape, unrolls itself and is lost. The other does
not stir from its posture of defence and resists successfully. Is this
due to acquired caution? No, but to the impossibility of doing otherwise
on the slippery surface of a table. Clumsy, obese, weak in the legs,
curved into a hook like the common White Worm (The larva of the
Cockchafer.--Translator's Note.), the Anoxia-larva is unable to move
along a smooth surface; it writhes laboriously, lying on its side. It
needs the shifting soil in which, using its mandibles as a plough-share,
it digs into the ground and buries itself.
Let us try if sand will shorten the struggle, for I see no end to it
yet, after more than an hour of waiting. I lightly powder the arena.
The attack is resumed with a vengeance. The larva, feeling the sand, its
native element, tries to escape. Imprudent creature! Did I not say that
its obstinacy in remaining rolled up was due to no acquired prudence but
to the necessity of the moment? The sad experience of past adversities
has not yet taught it the precious advantage which it might derive from
keeping its coils closed so long as danger remains. For that matter,
on the unyielding support of my table, they are not one and all so
cautious. The larger seem even to have forgotten what they knew so well
in their youth: the defensive art of coiling themselves up.
I continue my story with a fine-sized specimen, less likely to slip
under the Scolia's onslaught. When attacked, the larva does not curl up,
does not shrink into a ring as did the last, which was younger and only
half as large. It struggles awkwardly, lying on its side, half-open.
For all defence it twists about; it opens, closes and reopens the great
hooks of its mandibles. The Scolia grabs it at random, clasps it in
her shaggy legs and for nearly a quarter of an hour battles with the
luscious tit-bit. At last, after a not very tumultuous struggle, when
the favourable position is attained and the propitious moment has come,
the sting is implanted in the creature's thorax, in a central point,
below the throat, level with the fore-legs. The effect is instantaneous:
total inertia, except of the appendages of the head, the antennae and
mouth-parts. I achieved the same results, the same prick at a definite,
invariable point, with my several operators, renewed from time to time
by some lucky cast of the net.
Let us mention, in conclusion, that the attack of the Interrupted Scolia
is far less fierce than that of the Two-banded Scolia. The Wasp, a
rough sand-digger, has a clumsy gait; her movements are stiff and almost
automatic. She does not find it easy to repeat her dagger-thrust. Most
of the specimens with which I experimented refused a second victim on
the first two days after their exploits. As though somnolent, they did
not stir unless excited by my teasing them with a bit of straw. Although
more active and more ardent in the chase, the Two-banded Scolia likewise
does not draw her weapon every time that I invite her. For all these
huntresses there are moments of inaction which the presence of a fresh
prey is powerless to disturb.
The Scoliae have taught me nothing further, in the absence of subjects
belonging to other species. No matter: the results obtained represent no
small triumph for my ideas. Before seeing the Scoliae operate, I said,
guided solely by the anatomy of the victims, that the Cetonia-, Anoxia-
and Oryctes-larvae must be paralysed by a single thrust of the lancet;
I even named the point where the sting must strike, a central point,
in the immediate vicinity of the fore-legs. Of the three genera of
paralysers, two have allowed me to witness their surgical methods, which
the third, I feel certain, will confirm. In both cases, a single thrust
of the lancet; in both cases, injection of the venom at a predetermined
point. A calculator in an observatory could not compute the position of
his planet with greater accuracy. An idea may be taken as proved when
it attains to this mathematical forecast of the future, this certain
knowledge of the unknown. When will the acclaimers of chance achieve a
like success? Order appeals to order; and chance knows no laws.